Differential vacuum pump



April 22, 1930. D. N. CROSTHWAIT. JR

DIFFERENTIAL VACUUM PUMP Filed Aug. 1, 1927 I ""1". 'I/II'IIIIIIIIIIIIIIIIIllllll "11",. 111,111111111111,11,11,11,n.

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April 22, 1930.

n. N. CROSTHWAIT. JR 1,755,430

DIFFERENTIAL VACUUM PUMP I Filed Aug. 1, 1927 5 Sheets-Sheet 2 mm ma April 1930. D. N. CROSTHWAIT, JR 1,755,430

DIFFERENTIAL VACUUM PUMP Filed 1927 5 Sheets-Sheet 4 jimmy April 22, 1930.

Fil E- 1, 27 5 Sheets-Sheet 5 mww WNW m Patented Apr. 22, 1930 UNITED STATES PATENT OFFICE.

' DAVID N. CROSTHWAIT, JR., OF MARSHALLTOWN, IOWA, ASSIGNOR TO C. A. DUNHAM COMPANY, OF MARSHALLTOWN, IOWA, A CORPORATION OF IOWA ing DIFFERENTIAL VACUUM PUMP A uaumi filed August 1, 1927. Serial No. 209,775.

This invention relates to improvements in vacuum producing apparatus, and more particularly to an improved form of high speed provide an improved pumping apparatus for producing a vacuum, of the type briefly referred to hereinabove and disclosed more in detail in the description which follows.

Another object is to provide a pump of this type, that is simple in construction, eflicient and economical in operation and capable of drawing in a large amount of air or produchi h suction without consuming a great deal of power.

Other objects and advantages of the invention will be apparent from the. following detailed description of one approved form of the apparatus.

In the accompanying drawings:

Fig. 1 is an elevation showing the principal elements of a vacuum steam heating system for use in which this vacuum pump is especially designed.

Fig. 2is a central vertical section-through the pump and associated parts.

Fig. 3 is a front elevation of the pump unit.

Fig. 4 is a section through the pump unit, looking up from beneath, as indicated by the dotted line 4-4 of Fig. 3.1

Fig. 5 is a sectional view similar to Fig. 4, but taken on the dotted line 5-5 of Fig. 3, looking in the direction of the'arrows.

Fig. 6 is anelevation-of the impeller, parts being broken away to indicate the interior construction.

Fig. 7 is a diagrammatic elevation of the pump, with parts broken away so as to illustrate the relative positions of the interlocking water-circulating systems.

Fig. 8 is a diagrammatic sectional view adapted to illustrate the cycle of operations in one of the pump units.

Referring first to Fig. 1, the heating system The in which this pumping mechanism is designed to function will be briefly described. The steam generator A furnishes steam through the supply main B and inlet valves C to the radiators D. Condensate and air are drawn out of the radiators through the thermostatic traps E into the return main F. At G is indicated the improved vacuum producing mechanism with which the present invention is particularly concerned, this pumping mechanism being designed to exhaust air from the return main and also throughout the system when the heating system is operated at subatmospheric pressures. The means indicated generally at. H controls the vacuum producing. mechanism G so as to maintain a fixed difi'erence in pressure between the supply and return mains.

The generator A may be heated in any approved manner, preferably by means of an automatic gas heater which is thermostatically controlled in accordance with the temperature requirements in the space to be heated. This portion of the heating system is not here illustrated, but this heating system is more completely set forth and described in the copending application of Clayton A. Dunham, Serial No. 171,616, filed Feb. 28, 1927, now Patent No. 1,644,114, granted Oct. 4, 1927. Steam is supplied from the main B through risers 1 and inlet valves C to the radiators D, and condensate and air passthroughthe thermostatic traps E and pipes 2 to the return main F. Return main F is provided with the one-way valve 3, and is connected directly with pipe 4, which in turn is'connectcd with the boiler above and below the water level therein, so that liquid condensate in the return main will gravitate directly into the boiler. An air eliminator 5 of any approved form, having-an air check valve 6 is connected with return main F above the normal water level therein, so-as to vent air and gases from the return main when the system is operated above atmospheric pressure. A drip pipe 7 leads from the end of supply main B into the return main F beyond the one-way valve 3. Air is vented from drip pipe 7 through pipe 8 and trap 9 into the upper portion of return main F, fromwhich it is vented through air eliminator 5, as already described.

The improved pumping mechanism G, which will be described in detail hereinafter, is designed to withdraw air through pipe 10 from the return main F, and thus reduce the pressure in the system. The automatic control mechanism H (which is shown more in detail in Fig. 2) is designed to open and close the switch 11 which starts and stops the pump motor 12. This controller comprises a movable diaphragm 13 positioned in a housing 14, the spaces within this housing at either side of the movable diaphragm being connected by pipes 15 and lGrespectively with the supply and return-mains B and F. In this manner, the diaphragm 13 is subject on its opposite sides to the pressure existing in the supply and return mains, and when any material departure is made from a fixed ratio between these two pressures, the movement of the diaphragm 13 will through lever mechanism 17 and line 17 operate the electric switch 11. Vhen the difference in pressure between these two mains falls below a certan minimum, switch 11 will be closed, whereupon the motor 12 will be started and the pumping mechanism hereinafter described, will operate to withdraw air from the return main F and thus lower the pressure in the return side of the system. lVhen the desired maximum pressure diflerence has been re-established between the supply and return mains, the resulting movement of diaphragm 13 will operate to open switch 11 and thus stop the pump operating motor 12.

When starting the operation of this heating system, the fire will be started under gen erator A, and the pumping mechanism G will be put in operation. Since the system is cooled and empty of steam, the thermostatic traps E will be open and the vacuum created by the suction of pumping mechanism G will extend throughout the system and into the generator A, thus lowering the tem erature at which steam will be generated. T is subatmospheric steam will pass through supply main B and risers 1 into the radiators D, and as soon as steam attempts to pass the thermostatic traps E, they will close, thus trapping the steam within the radiators. The pumping mechanism G will continue to operate until the pressure within the return main F has been reduced the desired amount below the sub-atmospheric pressure existing in the supply main B, whereupon the control mechanism H will automatically stop the pumping mechanism G. As the steam condenses in the radiators D, the pressure in the radiators will be lowered, thus accelerating the generation of steam and causing more steam to pass into the radiators. By properly controlling the fires under the generator A, any sub-atmospheric pressure may be maintained in the supply side of the system. As condensates and air accumulate in the radiators D, the traps E will temporarily open and permit this liquid and air to escape into the return main F, the air being withdrawn by pumping mechanism G, or vented through air eliminator 5, and the water gravitating into the boiler through pipe 4.

The improved pumping mechanism G which forms the particular subject matter of the present invention, will now be described more in detail. The main casting 18 is formed with an air separating chamber 19, and a platform 18*. On the upper side of the platform 18 is supported the control. mechanism H, and the pump operating motor 12 is hung from the lower side of this platform. The casting 18 and the parts carried thereby may be supported at any suitable height by a stand consisting of the pipe sections 20, as indicated in Fig. 1. The drive shaft 21 of motor 12 is connected through coupling 22 with the impeller shaft 23 of the pump. This impeller shaft is provided with a main supporting bearing in the bracket arm 24 extending down from casting l8, and also has a bearing in the bushing 25 mounted in the depend- 7 in bushing 25. A packing ring 30 at the outer end of bushing 25 is held in place by the nut or gland 31 adjustably screwed onto the outer end of the bushing.

The impeller 32 (best shown in Figs. 4, 5 and 6) is keyed to the outer end of shaft 23, and is housed for rotation within an impeller casing, the back wall of which is formed by the web 26, and the remaining portion within a casting 33 mounted on web 26 by means of bolts 34. A suitable gasket35 seals the joint between the casting 33 and the web 26. The hub portion 36 of the impeller 32, which is keyed to the shaft 23-supports a laterally ofiset portion comprising the spaced parallel webs 37 and 38, which are connected at intervals by the substantially radial blades 39, thus forming passages or channels 40 which are open at their inner ends 41 and also at their outer ends 42. Another offset web 43 is connected with intermediate'web 38 by a plurality of blades 44 so as to form another series of passages or channels 45 which are also open at their inner. ends, but open into a space of greater diameter than that into which the channels 40 open at their inner' ends. The web 38 is of lesser diameter than the webs 37 and 43 so that the outer portions of channels 40 and 45 communicate with one another, as indicated at 46, the outer portions of the blades 39 and 44 being integraL- In order that the operation-of this pumping mechanism may be more quickly underwater passes into the outer ends of the chan- "nels from the passages 45, and after fill- 'ing the passage 40,'is expelled through the outer port 42. Assuming that the channel 40 is first filled with water and that the impeller is rotating in the direction of the arrow, this water will first bethrown out through the port 42, thus drawing in a charge of air from the space that is to be exhausted. Subsequently, a new charge of water is forced into the assage 40 from the channel 45, thus expelling the air through the port 41. This cycle of operations takes place twice in each channel 40 during every revolution of the impeller 32.

The casting 33' comprises an outer shell which encloses the impeller, and hub portions 47 and 48, which fit within the successively offset portions of the impeller. An air inlet chamber 49 communicates through passages 50 with the air inlet ports 51 extending through diametrically opposite sides of the hub 47 and adapted to communicate with the inner ports 41 of channels 40. An air outlet chamber 52 connects with air outlet ports 53 which are also disposed at diametrically opposite sides of the hub 47, but spaced substantially 90 degrees from the inlet ports 51.

A manifold 54 is attached at its lower end to the impeller casing 33, as by means of bolts 55, and contains an air inlet chamber 56, and an air outlet chamber 57, which communicate, respectively, with the chambers 49 and 52 in the casing 33. The exhaust pipe 10 leading from the return mam of the heating s stem opens into the chamber 56. An air discliarge conduit 58 in the manifold 54 leads from the chamber 57 and opens at its upper end into the air separating chamber 19. This completes the air circulating portion of the apparatus. Another passage 59 in the manifold 54 leads from the lower portion of chamber 19 into the air inlet chamber 49, but this is for the purpose of admitting additional water to the system and is not, properly speaking, an air conduit.

For the purpose of permittlng the clrculation of water, the casing 33 is formed w th J two substantially duplicate water passages 60 and 61 spaced 180degrees from one another, and overlapping, as best indlcated in Figs. 3 and 7. The channel 60 has an inlet port at 62 adapted to receive Water from the outer ports 42 of certain of the channels 40.

From this inlet opening the channel 60 leads inwardly and circumferentially around the casing to a discharge port 63 formed in the hub 48 and communicating with the inner ends of certain of the channels 45in the im-' peller. In an exactly similar manner the water channel 61 leads from an inlet port 64 to a discharge port 65, also positioned in the hub 48 at-a point diametrically opposite from the discharge port 63. It might be stated at this point that each of these channels 60 and 61 forms'part of a distinct and separate water circulating system, that is the water that is discharged from port 63, after passing through certain of the impeller channels 45 and 40, is again received through port 62 back into the channel 60. The same holds true of the water circulating in channel 61 which is discharged from and returned back into this same channel. However, each pair of channels 45 and 40 in the impeller successively receive and discharge water from each of the two water circulating systems 60 and 61 in alternation. That is, during each rotation of the impeller, each pump unit 40 receives and expels a charge of water from each of the two water circulating systems 60 and 61.

The operation of this pumping mechanism will best be understood from an inspection of 8. It will be understood that the impeller isrotated rapidly in the direction of the arrow. The channel 40, indicated at position K, is now completely filled with water, but its inlet port 41 is closed by the hub 47, and, its outlet port 42 is closed by the casing 33. When this channel 40 has reached the position M, its outlet port will be in communication with the inlet port 62 or 64 of one of the water channels 60 or 61, and the charge of water within the channel 40 will be thrown outward by centrifugal force into this water port 41 will come into communication with I one of the air inlet ports 51 in hub 47 and a charge of air will be sucked into this channel 40 as the Water is thrown outwardly. This action will continue through the positions 0 and P, so that when the channel 40 has reached the position Q substantially all of the water will be expelled and the channel will be filled with air. At this time, the channel 40 will be closed at its inner and outer ends, substantially as in the position K. It will be noted that this cycle of events has taken place during substantially 90 degrees, or one-quarter of a rotation of the impeller. The water that has been thrown into the channel v6O now passes around through this conduit until it reaches the discharge port 63 which is now in communication with one of the channels 45 at the position RI The water will be thrown outwardly through the channel 45 by centrifugal force, plus the impetus which the water has acquired during its passage through the conduit 60. This water will i be thrown around through the outer passage channel 40 has reaehedthe position S so that its inner end is in communication with the 'It should be noted that the air that is expelled at positions S, T and U is not the same 'charge of air that was drawn in at positions M, O and P, but a different charge of air that was drawn in during the operation of the other water circulating system, which operates during the other 180 degrees of the rotation. The other water circulating system operates in an exactly similar manner during the other half of the rotation of the impeller, and the manner in which these two systems overlap and cooperate will be understood from an inspection of Fig. 7. It will be noted that the water pistons are successively provided in alternation by the two water circulating systems, but that the charge of air drawn in by the water piston from one circulating system is expelled by the water piston furnished from the other water circulating. system, and vice versa.

The .air thus expelled intochamber 52 passes out into manifold chamber 57 and thence through passage 58 into the air separating chamber 19. In operation, some water will be discharged with the air in an atomized form, and this water will settle in the separating chamber 19, the air being vented through the normally open port 65and pipe 66,.which latter may be provided with a oneway check valve 67, as indicated in Fig. 1.

The pumping system is first primed with suflicient water to fill the water circulating passages and also leave a certain amount within the chamber 19, as indicated in the drawings. The same water normally circulates through the pump conduits. Only suflicient water needs to be added to this circulating system to replenish that which passes out with theair discharged through conduit 58. Some of this water will come in in the form of condensate from the return pipe of the heating system, through pipe 10. The remainder of this water is furnished through outlet passage 68 and conduit 59 in ieo manifold 54, from the reserve supply in chamber 18. The entrance to passage 68 is controlled by a slide-valve 70 having a tapered opening 71, so that the amount of water passing out through passage 68 may be controlled by raising or lowering valve 70. Valve 70 is controlled through link 72 from a floatoperated lever 73 within the tank or chamber 19. A valve 74, adapted to close the air vent 65, is also controlled from float-operated lever 73 through link 75. Another water outlet port 76 in the chamber 19 communi cates with a pipe'77 provided with checkvalve 77 through which water may be discharged back to the boiler of the heating system. A valve 78 swiveled on one arm of a bell crank 9, pivoted at 80 within the chamber 18, normally closes the outlet passage 76. The other arm 81 of this bell crank 79 is adapted to be engaged by the head 82 of valve 70 when this latter valve is sufliciently elevated. Normally the bell crank 79 is unsupported and its weight will hold the valve 78 in closed position at the inlet port of passage 7 6.

In normal operation the valve 78 will remain closed, and the valve 70 will be opened just sufiiciently to permit enough water to pass from chamber 19 through conduit'59 to replenish the amount that is withdrawn from the water circulating system with the air expelled through conduit 58. If more water is withdrawn from the circulating system, the

added accumulation in chamber 19 will raise the float and thus cause a further opening of the valve 70 to permit more water to return.

to the water circulating system. Since some condensate from the heating system will continually be drawn into the pumping apparatus with the air (although this apparatus is not intended to handle the liquid condensate,

and the only water which entersthe system will be that held in suspension in the air drawn out through pipe 10,) the accumulation of water in chamber 19 will gradually increase so that eventually the head 82 of valve 70 will engage the bell crank 79 and open the valve 78. At this time the valve 7 4 will close the air vent 65 so that the air pressure formed in chamber 18 will force the excess water off through passage 76 and pipe 77 back to the boiler. When the excess liquid has been removed, the float will again fall, opening the valve 7 4 and closing the valve 78 and the apparatus will function as before. It should be noted that the casing channels 60 and 61 each increase progressively in cross sectional j area from the inlet to the outletport so as to peller and easing except-at the entrance and outlet ports.

The design is such that the water passes entirely out of the impeller channels on each .suction stroke so as to draw in the maximum volumn of air. 1 This also permits the maxi a rotary impeller formed with a circular series of substantially radial channels provided with open ports at their inner and outer ends, and an impeller casing formed with alternate air inlet and discharge channels positioned to communicate with the inner impeller ports, and channels for circulating a liquid from certain of the outer impeller ports to other circumferentially spaced outer impeller ports, portions of said liquid channels being formed in the casing and portions in the impeller.

2. A fluid pumping apparatus comprising a rotary impeller formed with acircular series of substantially radial channels pro-. vided with open ports at their inner and outer ends, and also with an auxiliary series of channels positioned in substantially parallel relation with the first series, each adjacent pair of channels in the two series being in open communication at their outer ends, the inner end of each auxiliary channel being provided with an inlet port, and stationary.

means formed with conduits for conducting air to and from the inner ports of the radial impeller channels, and also with conduits for conducting liquids from the outer ports of the radial channels to the inlet ports of the auxiliary channels.

3. A fluid pumping apparatus comprising a rotary impeller formed with a circular se-. ries of substantially radial channels provided with open ports at their inner and outer ends, and also with an auxiliary series of channels positioned in substantially parallel relation with the first series, each adjacent pair of channels in the two series being in open communication at their outer ends, the inner end of each auxiliary channel being provided with an inlet port, and an impeller casing formed with alternate air inlet and discharge conduits positioned to communicate with the inner ports of the radial impeller channels, and with conduits for circulating a liquidfrom the outer impeller ports to the inlet ports of circumferentially spaced auxiliary impeller channels. I

4. A fluid pumping apparatus comprising a rotary impeller formed with a circular series of substantially radial channels provided with open ports at their inner and outer ends, andalso with an auxiliary series of channels positioned in substantially paralair ports being arranged in alternation and spaced substantially 90 apart, and a pair of liquid circulating conduits in the casing, each liquid conduit communicating at its inlet end with certain of the outer ports of the radial impeller channels, and communicating at its outlet end with the inlet ports of substantially diametrically opposed auxiliary channels.

5. A fluid pumping apparatus comprising a rotary impeller formed with a circular series of substantially radial channels provided with open ports at their inner and outer ends, and also with an auxiliary series of channels positioned in substantially parallel relation with the first series, each adjacent pair of. channels in the two series being in open communication at their-outer ends, the inner end of each auxiliary channel being provided with an inlet port, and an impeller casing formed with air inlet and discharge chambers and a pair of ports leading from each chamber and positioned to communicate with the inlet ports of the radial impeller channels, these inlet and discharge air ports being arranged in alternation and spaced substantially 90 apart, and a pair of liquid circulating conduits in the casing, each liquid conduit communicating at its inlet end with certain of the outer ports of the radial impeller channels, and communicating at its outlet end with the inlet ports of substantially diametrically opposed auxiliary channels, the liquid channels increasing in crosspectional area from their inlets to their outets.

6. A fluidpumping apparatus comprising an impeller casing, a drive shaft journaled in one wall of the casing, an impeller secured on the inner end of the shaft, the impeller having a laterally ofiset portion formed with substantially radial channels open at their inner and outer ends, the impeller casing and impeller being formed with passages for circulating liquid which communicate at spaced circumferential points with the outer open ends of the impeller channels, the impeller casing also being formed with air inlet and outlet passages which alternately communicape with the inner ends of the radial channe s.

- 7 A fluid pumping apparatus comprising an impeller casing, a drive shaft journaled in one wall of the casing, an impeller secured on the inner end of the shaft, the impeller having a laterally offset portion formed with a circular series of substantially radial channels open at their inner and outer ends, and with a second series of auxiliary channels which communicate with adjacent channels of the first series at their outer ends and are open at their inner ends, the casing having a portion projecting within the offset portion of the impeller and formed with air inlet and discharge passages which have ports communicating at spaced circumferential points with the inner ends of the radial impeller channels, the casing also being formed with liquid conduits, each of which communicates at one end with the outer ends of the radial channels, and at its other end with the inner ends of the auxiliary channels.

8. A fluid pumping apparatus comprising an impeller casing, a drive shaft journaled in one wall of the casing, an impeller secured on the inner end of the shaft, the impeller having a laterally offset portion formed with a circular series of substantially radial channels open at their inner and outer ends, and with a second series of auxiliary channels which communicate. with adjacent channels of the first series at their outer ends and are open at their inner ends, the casing having a portion projecting within the offset ortion of the impeller and formed with air inlet and discharge passages which have ports communicating at spaced circumferential points with the inner ends of the radial impeller channels, the inwardly projecting portion of the casing also having liquid outlet ports which communicate with the inner ends of the auxiliary channels, and liquid conduits extending circumferentially of. the impeller to these latter ports from the outer ends of the radial channels.

9. In a fluid pumping apparatus a rotary impeller formed with a circular series of relatively long substantially radial channels open at their inner and outer ends, and a second substantially parallel series of relatively short channels which respectively open at their outer ends into the adjacent longer channels, and are open at their inner ends, and means for conducting air into and out of the inner ends of the longer channels, and for conducting a liquid from the outer ends of the longer channels to the inner ends of the shorter channels.

10. In a fluid pumping apparatus a rotary impeller formed with acircular series of relatively long substantially radial channels open at their inner and outer ends, and a second substantially parallel series of relatively short channels which respectively open at their outer ends into the adjacent longer channels, and are open at their inner ends,

and a non-rotary housing having alternating passages for conducting air to and from the inner ends of the longer channels, and having passages fpr conducting a liquid from the outer ends of the longer channels to the inner ends of the shorter channels.

11. In a fluid pumping apparatus a rotary impeller formed with a circular series of relatively long substantially radial channels open at their inner and outer ends, and a second substantially parallel series of relatively short channels which respectively open -at their outer ends into the adjacent longer channels,

and are open at their inner ends, the inlet.

of each auxiliary channel being in advance of its outlet in the direction of rotation of the impeller, and means for conducting air into and out of the inner ends of the longer channels, and for conducting a liquid from the outer ends of the longer channels to the inner ends of the shorter channels.

12. In combination a fluid pump comprising a rotary impeller, an impeller. casing having conduits for continuously circulating a liquid into and out of the impeller, and also having air inlet and discharge chambers communicating with the impeller, a separating tank, an air vent in the tank, a conduit'leading from the discharge chamber of the pump to the upper portion of the tank, and a water conduit leading from the lower portion of the tank to the air inlet chamber.

13. In combination a fluid Bump com rising a rotary impeller, an impe er casing aving conduits for guiding a liquid into and out of the impeller, and also having air inlet and discharge chambers communicating with the impeller, a separating tank, an air vent in the tank, a conduit leading from the discharge chamber of the pump to the upper ortion of the tank, and a water conduit lea ing from the lower portion of the tank to the air inlet chamber, a valve controlling the flow of water into this latter conduit, and a float in the tank controlling the valve.

14. In combination a fluid pump comprising a rotary impeller, an impeller casing having conduits for guiding a liquid into and out of the impeller, and also having air inlet and discharge chambers communicating with the impeller, a separating tank, an air vent in the tank, a conduit leading from the discharge chamber of the pump to the u per portion of the tank, a water conduit leasing rom the lower portion of the tank to the air inlet chamber, a valve controlling the flow of water into this latter conduit, a second water outlet in the tank, a valve normally closing this outlet, a normall open valve for closing the air vent, and a float in the tank for operatin the valves. DA D N. GROSTHWAIT, JR. 

